Pervious concrete is a type of concrete that is highly porous to allow water, for example from precipitation, to pass through the concrete. The use of pervious concrete will reduce runoff from a site and route the runoff into the earth or into a collection system. As such, the use of pervious concrete is consistent with ecologically sustainable construction practices. Pervious concrete may be used for parking lots, sidewalks, driveways, and roadways, as a few non-limiting examples.
The porous nature of pervious concrete is achieved by the materials that are put into the concrete. Specifically, pervious concrete is a mix of course aggregate, cement, water, chemicals and little to no sand. This mixture creates an open-cell structure in the concrete, which allows water to filter though the pervious concrete.
Pervious concrete has historically been used in a “ready mix” fashion, delivered to a jobsite and poured into an on-site form. Pervious concrete is unique in many ways including the long cure time to reach maximum strength; the cure time required to reach full strength is typically 28 days or longer. The pervious concrete material must be covered to reduce moisture loss and temperature controlled during the cure time. During this cure time the product does not provide maximum protection and is prone to dilution from water, cracking from stressing or reduced ultimate strength due to temperature.